Laminar rate sensor

ABSTRACT

A laminar fluidic angular rate sensor for sensing the rate of angular rotation of the sensor which includes a supply passageway; at least two receiver passageways; vents, at least one of which is located between the two receiver passageways and is aligned with the supply passageways; and a cavity which are of a configuration and location such that fluid flowing through the supply passageway forms a laminar fluid stream which is capable of being received by the receiver passageways in the laminar state. The Reynolds number of the fluid forming the laminar fluid stream is preferably within the rante of 200-1500.

United States Patent 1191 Rexford [4 1 Apr.'3, 1973 [s41 LAMINAR RATESENSOR 3,457,934 7/1969 Kinner ..137/s1'.5

3,469,593 9/1969 [75] Invent 2",? schemctady' 3,574,309 4/1971 Kinner..137/s1.s 3,636,964 1/1972 Colamussi 6:31 ..137/s1.5x [73] Assignee:General Electric Company, New 3,670,755 6/1972 Nardi ..l37l8l.5

York,N.Y. v Primary Examiner-Samuel Scott Flled: 1972 Attorney-Allen E.Amgott et al.

Appl. No.: 216,493

Related U.S. Application Data [62] Division of Ser. No. 878,824, Nov.21, 1969.

[52] U.S. Cl ..l37/81.5 [51] Int. Cl. ..F15c 1/18 [58] Field of Search..l37/8l.5; 235/201 [56] References Cited UNITED STATES PATENTS3,310,985 3/1967 Belsterling et a1. ..l37/8,1.5 X 3,362,421 l/1968Schaffer ..137/8 1 .5 3,429,323 2/1969 1 Mott ..137/8l.5 3,450,1456/1969 Colston 1 37/8 1.5

[57] ABSTRACT A laminar fluidic angular rate sensor for sensing the rateof angular rotation of the sensor which includes a supply passageway; atleast two receiver passageways; vents, at least one of which is locatedbetween the two receiver passageways and is aligned with the supplypassageways; and a cavity which are of a configuration and location suchthat fluid flowing through the supply 4 Claims, 9 Drawing Figures sum 1[1F 3 LAMINAR RATE SENSOR This is a division, of application Ser. No.878,824, filed Nov. 21, 1969.

BACKGROUND OF THE INVENTION The subject invention generally relates tothe area of fluidics and, in particular, to fluidic angular rate sensorswhich utilize a laminar flow stream.

Conventional state-of-the-art fluidic devices generally utilize aturbulent (i.e., non-laminar) fluid stream flowing from one or moresupply passage ways to one or more receiver passageways. Such aturbulent fluid stream may assume a substantially linear or vorticalpath. Fluidic devices of this kind require a substantial pressure headof fluid and are inherently of very low efficiency with a lowsignal-to-noise ratio, due to the turbulence of the fluid stream.Turbulence amplifiers had been developed in which a laminar fluid streamis initially formed and flows from a supply passageway toward an alignedreceiver passageway, and means are provided for causing the fluid streamto become turbulent in response to a control signal. Turbulenceamplifiers are characteristically slow in response time due to therecovery time necessary to form a laminar fluid stream from a turbulentfluid stream once the control signals have been removed and also have alow signal-to-noise ratio.

SUMMARY OF THE INVENTION Therefore it is an object of the subjectinvention to provide a fluidic angular rate sensor utilizing andmaintaining a laminar fluid stream.

Another object is to provide a laminar fluidic angular rate sensorhaving a high signal-to-noise ratio at high efficiency.

The above-stated objects are fulfilled in the subject invention byproviding a laminar fluidic angular rate sensor comprises of avsubstantially linear supply passageway for forming a laminar fluidstream, the length of the supply passageway being at least ten times thesmallest cross-sectional dimension of the nozzle portion of the supplypassageway; at least two substan tially linear receiver passagewayscapable of receiving the laminar fluid stream and having across-sectional area no less than that of the nozzle portion; a closedcavity between the supply and receiver passageways; and venting means incommunication with the cavity and located, at least in part, between thereceiver passageway for helping to maintain the fluid stream in thelaminar state.

The subject matter which is regarded as the present invention isparticularly pointed out and distinctly claimed in the concludingportion of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention, however,together with further objects and advantages thereof, may best beunderstood by reference to the following description taken in connectionwith the accompanying drawings in which:

FIG. 1 is a schematic representation of a laminar fluidic proportionalamplifier in accordance with the subject invention;

FIG. 2 is a cross-sectional view of the device shown in FIG. 1 takenalong the line denoted II-II;

FIG. 3 is a schematic view of a laminar fluidic digital amplifier inaccordance with the subject invention,

FIG. 4 is a cross-sectional view of the device shown in FIG. 3 takenalong the line denoted IVIV;

FIG. 5 is a schematic view of another embodiment of laminar fluidicdigital amplifier in accordance with the subject invention;

FIG. 6 is a schematic representation of a laminar fluidic OR gate inaccordance with the subject invention;

FIG. 7 is a schematic representation of a laminar fluidic AND gate inaccordance with the subject invention;

FIG. 8 is a schematic representation of a laminar fluidic angular ratesensor in accordance with the subject invention; and

FIG. 9 is a cross-sectional view of the device shown in FIG. 8 takenalong the line denoted IX IX.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. 1 and 2 a schematicrepresentation of a laminar fluidic proportional amplifier 10 is shown.Amplifier 10 is formed by a plurality of laminated plates 12, 14, 16,18, 20. Top and bottom plates 12, 20 are used as cover plates and centerplates 14, 16, 18 have had portions removed therefrom by any suitablemeans, such as etching, drilling, coining, etc., to provide the desiredstructure.

The structure is comprised of a supply passageway 22 having a nozzleportion 24, an interaction cavity 26, two receiver passageways 28, 30,three vent passageways 32, 34, 36, and a pair of control passageways 38,40.

Supply passageway 22 is used to form a laminar fluid stream denoted 42flowing through cavity 26. Supply passageway 22 is substantially linearin shape and should be of a length at least ten times the smallestcross-sectional dimension of nozzle portion 24. The cross section ofsupply passageway 22 is preferably uniform along its length and may beof any desirable shape such as circular, oval, rectangular or square.For purposes of illustration, the passageways shown in the figures arerectangular in cross section. For the embodiments shown in FIGS. 1 and 2the smallest crosssectional dimension of nozzle portion 24 would be theheight of the passageway at that point. If desired, passageway 22 may beslightly tapered.

Control passageways 38, 40 terminate adjacent the laminar fluid streamdownstream of nozzle portion 24 and are preferably positioned upstreamof the cavity so that the action of the control fluid in passageways 38,40 on laminar fluid stream 42 serves only to deflect the stream and notto cause turbulence therein. The deflection of fluid stream 42 bycontrol fluid in passageways 38, 40 is controlled by the difference inpressures between the control fluids in the two control passageways withlittle if any mixing of the control fluids with the fluid of the laminarfluid stream. To best effect this, it is preferable that the height ofthe control passageways be the same as the height of the nozzle portion.Also, it is generally desirable, depending upon the pressures of thefluids involved, and the desired sensitivity, to have the width of eachcontrol passageway greater than the width of nozzle portion 24,

for example 1% 2 times as large. While each control passageway 38, 40 isshown to be at a right angle to supply passageway 22, this angularrelationship is not necessary.

Interaction cavity 26 is closed, that is, it is connected only to thesupply and receiver passageways and the vents and in an indirect mannerto the control passageways. The configuration of cavity 26 is such thatthe laminar fluid stream flows therethrough while remaining in thelaminar state.

For proper operation of the subject device, the fluid comprising fluidstream 42 should have a Reynolds number between 200 and 1,500 and theheight of cavity 26 should either be greater than ten times the heightof nozzle portion 24 or it should be substantially the same height asthat of nozzle portion 24. For cavity heights between one and ten nozzleheights the fluid stream has a tendency to attach itself to the top orbottom of the cavity, while for nozzle heights less than one nozzleheight turbulence can occur at the step from the nozzle to the shallowercavity.

Two substantially linear receiver passageways 28, 30 are provided with acentral vent passageway 34 located therebetween and vent passageways 32,36 located on the other side of each receiver passageways 28, 30,respectively. The three vent passageways make up the ventingmeans forthis embodiment with the central vent passageway 34 being substantiallyaligned with supply passageway 22. Generally it is desirable that thecross-sectional area of receiver passageways 28, 30 at their fluid inputportion be at least as large as the crosssectional area of nozzleportion 24, and preferably 1% 2 times as great. Receiver passageways 28,30 are configured so that the laminar fluid stream 42 can flowtherethrough with little impedance. It is therefore desirable that thepassageways be either of substantially constant cross-section or slightdivergent.

Vent passageways 32, 34, 36 are of a configuration such that there issubstantially no impedance to fluid flow therethrough to preventdisturbance of laminar fluid stream 42. It is undesirable for the ventpassageways to either impede the flow of fluid or pull fluidtherethrough as a result of venturi suction caused by an unrestricteddiffusion in the vent. In effect, the vent passageways should act asopen windows. In order to maintain fluid stream 42 in laminar state, theventing means should be provided adjacent and as close as possible tothe upstream portion of the receiver passageways.

The output of proportional amplifier is a pressure differential in thereceiver passageways proportional to the difference in fluid pressuresin control passageways 38, 40. In operation, a pressurized fluid with aReynolds number less than 1,500 and preferably between 200 and 1,500 issupplied to supply passageway 22 to form laminar fluid stream 42.Control fluid, ducted to control passageways 38, 40 acts on laminarfluid stream 42 exiting from nozzle portion 24 to deflect that streamproportionally to the difference in pressures of the control fluid inthe control passageways. If the pressures are equal, the stream will notbe deflected and most of fluid stream 42 will enter central vent 34 witha substantially equal percentage of fluid entering receiver passageways28 and 30, thereby providing a zero pressure differential output. If,for extional dimension of the nozzle portion, as the laminar fluidstream 42 begins to become marginally stable at greater lengths. I

The embodiment shown in FIGS. 3 and 4 is one form of laminar fluidicdigital amplifier. The structure shown is similar to that shown in FIGS.1 and 2 with similar structured supply passageway 22, controlpassageways 38, 40 receiver passageways 28, 30 and vent passageways 32,34 and 36. The major difference is that wall means 44 are providedbetween control passageways 38 and a cavity 46. Wall means 44, whichincludes two wall surfaces, defines, in part, a channel 48 having aheight substantially equal to that of nozzle portion 24. Channel 48, atleast a portion of which is divergent, has a minimum width no less thanthe width of the nozzle portion 24. The wall surfaces are positionedsuch that when the fluid stream becomes at tached to one of wallsurfaces 44, the fluid stream flows substantially directly through oneof receiver passageways 28, 30 depending onto which wall surface it isattached.

In this embodiment cavity 46 is shown as having a height substantiallyequal to the height of nozzle portion 24. However, as explained above, acavity having a height at least 10 times as great as the height ofnozzle portion 24 may also be used.

In operation, the digital amplifier shown in FIGS. 3 and 4 acts as abi-stable device with fluid stream 42 being stable only when it isattached to one of wall sur faces 44. When the pressure of the controlfluid in one of the control passageway, for example 40, is greater thanthe pressure in the other control passageway, fluid stream 42 isdeflected so as to become attached, by the wall attachment effect, to awall surface 44, in this example, the lower one, and exits primarilythrough one of the receiver passageways, in this example passageway 28.Fluid stream 42 remains this way until the pressure of the control fluidin the other control passageway, passageway 38, becomes sufficientlygreater than the pressure in control passageway 40 to cause fluid stream42 to be deflected away from the lower wall surface. Fluid stream 42then becomes attached to the other wall surface 44, the upper one, andexits primarily through the other receiver passageway, passageway 30.Fluid stream 42 remains laminar throughout the operation of the device.Such a bi-stable device is commonly known as a flip flop. 1

In FIG. 5 another embodiment of laminar fluidic digital amplifier isshown. The apparatus in FIG. 5 differs from that shown in FIGS. 3 and 4principally from the standpoint of the venting means used. In place ofthe central vent passageway, 34, the device of FIG. 5 uses a centrallylocated cusp 50 arid a pair of vents 52,

54 located on opposite sides of interaction cavity 46. Cusp 50 is usedto deflect fluid which is not able to enter one of receiver passageways28, 30 to one of the vents 52, 54 without disturbing the laminar stateof fluid stream. For example, if the laminar fluid stream is attached tothe upper wall surface, the stream will be directed toward receiverpassageway 28 with most of the fluid flowing therethrough. A smallamount of the fluid stream including fluid from interaction cavity 46which is entrained therein will exit through vent passageway 32 and asmall amount will be deflected by cusp 50 and exit out through vent 54.Except for the venting, the operation of the device shown in FIG. 5 isexactly the same as the operation as the device shown inFIGS. 3 and 4.

In FIG. 6 a laminar fluidic OR gate is shown. In this device twosubstantially linear supply passageways 56, 58 angled in toward eachother are provided. Each supply passageway 56, 58 has its own nozzleportion 60", 62, respectively, and bears the same dimensionalrelationship therewith as supply passageway 22, discussed above. Theangle between supply passageways 56, 58 is preferably no greater than 45to insure that the fluid streams flowing from the supply passagewaysremain laminar. One central receiver passageway 64 with two ventpassageways 66, 68 adjacent thereto are provided. Cavity 70 is locatedbetween the receiver and vent passageways and the supply passageways.The inlet of receiver passageway 64 is substantially aligned with bothpassageways 56, 58 so that when fluid flows through eitheror both supplypassageways 56, 58 fluid flows out through receiver passageway 64 toprovide a fluid pressure signal. In the embodiments shown, cavity 70 aswell as all the passageways are shown to be of the same height, althoughcavity 70 may have a height at least 10 times the height of nozzleportion 60, 62.

In FIG. 7 a laminar fluidic AND gate is shown which utilizes a structuresimilar to the OR gate structure in FIG. 6. Like the OR gate structureshown in FIG. 6, supply passageways 56', 58' should have an angletherebetween no greater than 45. The difference between the structure ofthe OR gate of FIG. 6 and the AND gate of FIG. 7 lies in the alignmentof the receiver passageway 64 and vent passageways 66, 68 relative tosupply passageways 56', 58. In the structure shown in FIG. 7 each supplypassageway 56, 58 is aligned with a vent passageway 68, 66, respectivelyand receiver passageway 64 is aligned with a line substantiallybisecting the angle between supply passageways 56' and 58'. r

In operation, when fluid flows through either supply passageway 56 or58, the laminar fluid stream formed thereby exits through ventpassageway 68 or 67 with substantially no fluid flowing through receiverpassageway 64. When fluid flows through both supply passageways 56, 58'both laminar fluid streams are deflected to form a single laminar fluidstream which flows through receiver passageway 64 thereby providing afluid pressure indication of the presence of fluid flow in both supplypassageways.

Both the OR gate and the AND gate of FIGS. 6 and 7 are passive devicesin that the control fluid flow, which is the fluid flowing through thesupply passageways, directly provide the fluidic operation; i.e., theydo not act on a non-control fluid power stream.

shown in FIGS. 1 and 2, differing primarily in that no controlpassageways are provided. Supply passageway 22, cavity 26, receiverpassageways 28, 30 and vent passageways 32, 34, 36 are all provided. Theventing means for the angular rate sensor may also include additionalvents 72, 74 which communicate with cavity 26 nearnozzle portion 24.Supply passageway 22 is at least ten times as long as the smallestcross-sectional dimension of nozzle portion 24. Central vent passageway34 is aligned with supply passageway 22 and receiver passageways 28, aresymetrically placed with respect thereto.

In operation a pressurized fluid is caused to flow through. supplypassageway 22 to form a laminar fluid stream. Like all the embodiments,in order to provide a fluid stream in a laminar state it is preferablethat the fluid flowing through supply passageway 22 have a Reynoldsnumber of between 200 and l ,500. As the angular rate sensor is rotatedin the plane of the surface shown in FIG. 8 (which plane includesthe'exit of supply passageway 22 and the entrances of receiverpassageways 28, 30), laminar fluid stream 42 is deflected in a directionopposite to that of the rotation. For example, when the device is notbeing rotated, laminar fluid stream 42 will exit through central ventpassageway 34 with a substantially equal, but small amount exitingthrough receivers 28 and 30 thereby producing a zero pressuredifferential between the two receiver passageways 28 30. If the deviceis rotated in a clock-wise direction in the plane of the surface shownin FIG. 8, fluid stream 42 will be deflected so that more fluid entersreceiver passageway 28 than enters receiver passageway 30 therebyproviding a pressure differential between and within the two receiverpassageways which is proportional to the angular rate of rotation of thedevice within the plane. Preferably receiver passageways 28, 30 arelocated such that when the device is being rotated at the maximumangular rate to be sensed, substantially all the fluid stream will enterone of the receiver passageways 28, 30 depending on the direction of therotation. The use of the particular venting means shown helps to permitfluid stream 42 to remain in the laminar state even when the device isbeing rotated. Cavity 26 is shown as having a height at least ten timesas great as the height of nozzle portion 24. Alternatively cavity 26 maybe of substantially the same height as nozzle portion 24. The shapesofthe cavities shown in the figures are merely representative of theshapes that may be used, subject to the height limitation discussedabove. The shape of the cavity determines, at least in part, the ventingmeans that should be used to maintain the fluid stream in the laminarstate. i i

Many other embodiments and modifications, in addition to those discussedabove, are intended to be included within the scope of the subjectinvention.

Additionally, the subject invention may be used in vided by using afluid having a Reynolds number less than 1,500 and preferably between200 and 1,500 in a structure having two supply nozzle of a length atleast ten times as great as the smallest cross-sectional dimension ofthe nozzle end of the supply passageway, at least two linear receiverpassageway having a cross-sectional area at least as great as the nozzleportion and venting means, at least a portion of which is locatedadjacent the receiver passageway and being in communication with acavity located between the supply and receiver passageways to maintainthe fluid stream in a laminar state.

The scope of the subject invention is to be limited only by the appendedclaims.

What I claim and desire to secure by Letters Patent in the United Statesis:

l. A laminar fluidic angular rate sensing device for sensing the rate ofangular rotation of the device in a plane for use with a fluid having aReynolds number less than 1,500 comprising:

a. a substantially linear supply passageway having at its downstream enda nozzle portion for forming a laminar fluid stream, the length of saidsupply passageway being at least 10 times the smallest cross-sectionaldimension of said nozzle portion;

b. two substantially linear receiver passageways capable of receiving aportion of said laminar fluid stream from said supply passageway, thecross-sectional area of each of said receiver passageways being no lessthan the cross-sectional area of said nozzle portion;

. a substantially closed cavity located between said supply and receiverpassageways and through which said laminar fluid stream flows; and

. venting means in communication with said cavity a portion of which islocated between said receiver passageways for helping to maintain saidfluid stream flowing through said cavity in the laminar state bypresenting substantially no impedance to fluid flow therethrough;whereby rotation of said device in a plane which includes the exit ofsaid supply passageway and the entrances of said receiver passagewayscauses deflection of said laminar fluid stream to produce a pressuredifferential between and within said receiver passageways which isproportional to the angular rate of rotation of said device within theplane.

2. A device as in claim 1 wherein the height of said cavity issubstantially the same as the height of said nozzle portion.

3. A device as in claim 1 wherein the height of said cavity is at leastten times a great as the height of said nozzle portion.

4. A device as in claim 1 wherein the length of said cavity is nogreater than 50 times the smallest crosssectional dimension of saidnozzle portion.

1. A laminar fluidic angular rate sensing device for sensing the rate of angular rotation of the device in a plane for use with a fluid having a Reynolds number less than 1,500 comprising: a. a substantially linear supply passageway having at its downstream end a nozzle portion for forming a laminar fluid stream, the length of said supply passageway being at least 10 times the smallest cross-sectional dimension of said nozzle portion; b. two substantially linear receiver passageways capable of receiving a portion of said laminar fluid stream from said supply passageway, the cross-sectional area of each of said receiver passageways being no less than the cross-sectional area of said nozzle portion; c. a substantially closed cavity located between said supply and receiver passageways and through which said laminar fluid stream flows; and d. venting means in communication with said cavity a portion of which is located between said receiver passageways for helping to maintain said fluid stream flowing through said cavity in the laminar state by presenting substantially no impedance to fluid flow therethrough; whereby rotation of said device in a plane which includes the exit of said supply passageway and the entrances of said receiver passageways causes deflection of said laminar fluid stream to produce a pressure differential between and within said receiver passageways which is proportional to the angular rate of rotation of said device within the plane.
 2. A device as in claim 1 wherein the height of said cavity is substantially the same as the height of said nozzle portion.
 3. A device as in claim 1 wherein the height of said cavity is at least ten times a great as the height of said nozzle portion.
 4. A device as in claim 1 wherein the length of said cavity is no greater than 50 times the smallest cross-sectional dimension of said nozzle portion. 